Dark Energy Survey reports tightest estimates yet on cosmic expansion

The Dark Energy Survey released results from its six-year sky survey that combine four measurement methods and deliver constraints on cosmological parameters more than twice as precise as earlier DES analyses.

The Dark Energy Survey (DES) released a combined analysis of data from its six-year, wide-area survey that aimed to measure the Universe's expansion. The study brought together four independent probes used to estimate cosmic expansion and dark energy. DES collected observations over 758 nights with the 570-megapixel DECam on the Víctor M. Blanco 4-meter Telescope, mapping roughly 669 million galaxies across about one-eighth of the sky. The collaboration reports that the new analysis tightens constraints on cosmological parameters compared with earlier DES work. Key findings: - The analysis combines baryon acoustic oscillations, Type Ia supernovae, galaxy cluster counts, and weak gravitational lensing in a single, unified dataset. - The survey data were gathered over 758 nights using DECam and cover about one-eighth of the sky with roughly 669 million galaxies observed. - The combined constraints on expansion-related parameters are reported as more than twice as stringent as previous DES analyses. - DES tested two dark energy models, the standard ΛCDM and the wCDM model, and found the data fit both models similarly without decisively favoring one. - One parameter tied to galaxy clusters shows increased tension with model predictions compared with earlier clustering analyses. Summary: The new DES results narrow the range of viable cosmological parameters and refine measurements that relate to dark energy and the expansion history of the Universe. The DES Collaboration plans to combine these results with constraints from other dark energy experiments and with forthcoming data from the Vera C. Rubin Observatory's Legacy Survey of Space and Time to seek still tighter limits on cosmological models.